Reassuring news on mRNA vaccines for breastfeeding mums

Anastasia Tsirtsakis

7/07/2021 2:52:08 PM

A new study suggests the mRNA from COVID vaccines such as Pfizer and Moderna does not end up in breast milk.

Breastfeeding baby
The Pfizer mRNA vaccine is recommended for pregnant and breastfeeding women in Australia.

When the first doses of Pfizer’s COVID vaccine arrived on Australia’s shores back in February, GP and breastfeeding specialist at the Royal Women’s Hospital, Professor Lisa Amir, recalls some apprehension among her patients.
‘Everyone was concerned with this new type of vaccine because the messenger RNA (mRNA) is new,’ she told newsGP.
‘Mothers were asking, what should [we] do?
‘From first principles, we said this mRNA shouldn’t get into the breast milk. We vaccinate breastfeeding women with all the other vaccines, except yellow fever. So it would have been surprising if it wasn’t going to be safe.’
There now is further evidence to back that idea.
In a peer-reviewed study published in JAMA Pediatrics, scientists from the University of California tested breast milk from seven women before and after they had received an mRNA vaccine for COVID-19. Five women received Pfizer and two received Moderna.
Out of 13 samples of breast milk, they found there was no mRNA from the vaccines present following vaccination.
While larger studies are required to confirm the findings, the scientists say their results provide early evidence to back current recommendations that vaccine-related mRNA is not transferred from mother to baby via breast milk, and that women should not stop breastfeeding because they have had the vaccine.
Pfizer is currently the only COVID vaccine approved for use by the Australian Technical Advisory Group on Immunisation (ATAGI) for pregnant and breastfeeding women.
Professor Amir says the findings confirm what experts in the field already expected, but that the growing body of research will help GPs reassure their breastfeeding patients.
‘That’s what we would expect … so it’s not surprising. But it’s good to see evidence and that it’s been carefully carried out [by] a reliable university,’ she said.
‘And although seven women sounds small, that’s the sort of number that they do research like this on. Scientists say if it’s well conducted, then that’s enough, and it looks like this is very carefully done.
‘They separated the milk into what they call the fat layer and the supernatant [and] they’ve looked at each separately. So if there was any there, they would have detected it, and if there was any tiny bit that wasn’t detected, it would have been inactivated in the baby’s stomach if the baby ingests it.’
In addition to COVID vaccination being safe for breastfeeding women, Professor Amir says research is also showing that it can actually have benefits for their babies.
A few papers have come out saying that the antibodies the mother produces in response to the vaccine should appear in the breast milk, which is what, again, we would expect from first principles,’ she said.
‘If the individual who gets the vaccine is producing antibodies … they produce IgG that they measure in the blood, but the breast produces IgA.
‘It wouldn’t be enough to say that the baby has been immunised against COVID, but it’s enough to say that if a woman is breastfeeding and considering whether to have the vaccine, particularly whether they have one of the novel mRNA vaccines, that she shouldn’t have any concerns because one, the vaccine is not going to get into the milk, and two, the breast will produce some antibodies, which can be beneficial for the baby.’
While COVID vaccines in Australia are only available to particular cohorts, Professor Amir says GPs have an important role to play in encouraging vaccination for those who may be at higher risk of contracting the virus due to their profession and are breastfeeding.
‘People have been thinking first-line workers are doctors, nurses, midwives who might be dealing with patients who are positive, so they should be vaccinated. But we have seen that people who are working in admin roles or as cleaners – they’ve been a bit forgotten,’ she said.
‘GPs should be encouraging anyone in those situations to get vaccinated, even if they’re breastfeeding, because there’s no harm to them or their child.
‘Sometimes people don’t even tell the GP that they’re breastfeeding because they don’t want someone to tell them to stop. So, somehow, we have to get the message out there.’
An infographic featuring advice for breastfeeding mothers about the current COVID-19 vaccines is available on the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) website.
RANZCOG has also prepared answers to some commonly asked questions about COVID-19 vaccination and breastfeeding.
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